new Promise(resolve=>{
    setTimeout(()=>{
        let a = 'hello';
        resolve(a);
    },10);
}).then(value=>{
  return new Promise(resolve=>{
  setTimeout(()=>{
  let b = "lagou";
  resolve(value + b);
    })
  })
}).then(value=>{
  setTimeout(()=>{
  let c = "I ♥ You";
  console.log(value + c);
},10);
});